Repairing a crack and shrunken pickguard on 1970’s Martin D-35

A beautiful D-35 walked in the door, I repaired some unattached binding- then it came to my attention the shrunken pickguard had actually cracked the soundboard.. I had not planned on blogging this repair, so I didn’t take pics of the original binding repair or the heavy warpage of the pickguard. The project was challenging, but the outcome was worth the effort..  😉

Since the pickguard had let go around the edges and curled upward, it was pretty ugly. At the bottom edge it had curled up almost 3/8″ and become perpendicular to the top of the instrument. Where the glue was still intact, the shrinkage had pulled so hard against the wood that the wood cracked. This necessitated removal of the pickguard to unload the tension, as well as attempt to reverse the warpage,  repair the cracked wood beneath, and reattach it properly. That’s where this story begins..



I successfully removed the pickguard without damage to the substrate or the original finish.



The crack below the pickguard (right along the edge) was raised and unsupported from below.. the extended tiny crack was raised a bit, but is backed by the internal bridge plate, thus ugly- but stable.


This is the problematic area, right below the pickguard. Below is a shot of the same area with a high-power flashlight shining through the wood..


I then traced around the pickguard and made a template from 1/4″ Lexan- a smooth, fairly sigid plastic that will support the entire surface of the pickguard during glue-up.

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I raised the grain with a damp rag, to open the pores of the wood and allow the glue to penetrate deeper into the wood.20140626_051137


Then made sure the Lexan caul was a perfect fit to the body.


I cut pieces of thin card stock until the shape fit inside the instrument and avoided all the bracing. The pressure I need to get everything aligned and flat during gluing requires support from inside- there is no other way to get a flat, strong, permanent repair. Eventually, these shapes were cut from 3/4″ MDF and covered with waxed paper to keep the cauls from being glued inside the guitar (if glue seeped out).


Then I filled a hypodermic needle with wood glue, and injected/pushed glue into the voids. I worked from the interior and the exterior, using a flashlight, camera, and mirror.

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Once I was satisfied there was enough glue coverage, I applied the interior caul, a temporary Lexan caul, and a couple of clamps. Left that to dry completely.



As nicely as it turned out, I didn’t feel it was a strong repair. Yes, the crack was fixed, but further shrinkage of the pickguard over time would likely open up the repair- and it can only be glued one time. Cured glue will not stick to itself. Basically, do it right now.. One chance at it.

So I machined a little cleat from maple, with the grain running in the opposite direction, fitted it, and clamped/glued it in place. It is a very thin slice (about 1/32″ thick), but the crossgrain orientation and the natural strength of the maple will reinforce the top without significantly altering the sound of the instrument. Nice fit, tight, light, and strong. Mo’ better.. lol

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Pinpoint accuracy is key- don’t want anything rattling inside when I’m finished.


Once the cleat was in place and all excess glue had been cleaned, I painted the underside of the pickguard with Titebond glue and placed it carefully in its original footprint. Then I set the Lexan caul on top of the guard, and carefully fitted several clamps and interior cauls- adjusting the position along the way. Eventually, the entire pickguard was in place and flattened. Obviously, I try to clean up and excess glue as I go. The reason I chose Titebond as opposed to a solvent based glue is that Titebond is water based and will not damage the original finish. Wood fibers were still bonded to the underside of the pickguard- leftovers from the original attachment. The Titebond works great on wood, but not great on plastic. Since there was a coating of wood fibers stuck to the underside of the guard, the Titebond had plenty of wooden surface to create a durable bond.

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I let the assembly dry for about 6 or 7 hours, pulled the clamps and cauls, then cleaned off the remainder of the excess glue with a slightly damp rag. Then I hand polished the finish and the pickguard to restore the original shine.

I then polished the fret tops, cleaned the gunk off the fretboard, oiled the ebony, checked the inlays, and installed a fresh set of Martin strings.

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I’m very happy with the result, this is a great guitar. Looks better than if I had just squeezed some glue into the open crack and stuck a new pickguard on it- it looks, sounds, plays and feels “right”.  Gorgeous.  😉







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